ST1300 tow hitches are rarer than hen's teeth, finding one close by, and then in your state (QLD?) rarer again.
Having said that, there are at least two commercially made out there, Classic (made in Yandina, QLD) and Unigo (made in the USA). I've had both, the Unigo is far, far superior.
Classic hitches are good, had one my CB1300, and now have one my ST1300. The Unigo purchase was a stroke of luck back in 2013 when an OzSTOC member was selling it. When it arrived I knew immediately that it was a better design and build than the CB's Classic hitch. I had a rush of blood back in 2018 (I think) sold the Elite camper trailer and Unigo hitch. After another rush of blood in 2020, I bought another trailer and needed a hitch. Couldn't find a Unigo hitch, had to settle on a Classic hitch.
I have a couple of more motorcycle camping trips left in me (we were talking of this at yesterday's RTE) and then the trailer and tow hitch will be available, first of all as a package deal.
My most recent motorcycle camping trip was was to the OzSTOC 2022 NatRally at Mannum, SA. I was to have my last at the 2023 Cold Flame Rally at Native Dog Flat, VIC in Mar 2023, but had a little incident on the way there. Other circumstances have got in the way of my last hurrah, but I'm now planning this for Nov 2024.
If you can wait until late November, let me know if you're interested.